The present invention relates to a chain stitch sewing machine and, more particularly, to an in-line chain stitch sewing machine having a thread trimmer system which operates automatically below the needle plate.
The sewing machine of the present invention is used exclusively to form a chain stitch, which is well known in the art as a type 401 stitch, and is to be distinguished from machines forming other types of stitches such as, for example, a lock stitch formed by sewing machines disclosed in U.S. Pat. Nos. 3,139,849 and 4,401,046. The sewing machine of the present invention forms a chain stitch by using an in-line looper system which is distinguishable from a machine using a transverse looper system such as, for example, the machines disclosed in U.S. Pat. Nos. 3,354,852 and 3,532,065. A sewing machine using a transverse looper system forms the chain stitch by cycling through an elliptical path that is perpendicular to the direction of sewing. Because of the perpendicular relationship and ample space below the needle plate, trimmer systems cutting below the needle plate have been used on machines using the transverse looper system. The problem with using such machines, however, is that they are limited to about 5 needles and a small sewing width.
Machines using the in-line looper system, however, can use more than 30 needles and provide an unlimited sewing width. As such, they are more desirable for certain commercial applications. In such machines, however, the loopers move only in a straight line parallel machines, however, the loopers move only in a straight line parallel to the direction of sewing and, as such, require the use of an extra component, a set of coaxially aligned spreaders, to form the stitch by moving perpendicular to the direction of sewing. Because of the extra components, one spreader for each needle, there is little space for positioning an automatic thread trimmer system below the needle plate. Instead, thread trimmers typically have been positioned above the needle plate congesting the working space above the needle plate, such as, for example, the machine disclosed in U.S. Pat. No. 4,461,229. Accordingly, there is a need for an in-line thread trimmer system that automatically cuts the threads below the needle plate and, more specifically, one that cuts the last chain stitch being sewn in a first piece of material so that it does not unravel and then positions the tail end of the threads so that they are automatically set up for the first chain stitch in the next piece of material to be sewn.